The Islamist terror group ISIS’s big advantage is that it doesn’t fight conventionally. It’s held off the regular army of Bashar al-Assad and routed thousands of Iraqi troops. But now a group has emerged that turns ISIS’s tactics back against them.

The group is called White Shroud. There’s very little known about the group, but Syrian citizen journalism website Tahrir Souri reported on the group’s existence on July 24. According to the report, White Shroud is based in Abu Kamal near the border with Iraq, and the organization is associated with Syria’s melange of rebel forces, not the Assad regime.

It’s tactics include “secret assassinations, raids and surveillance” of ISIS targets, according to the report. The group uses improvised explosive devices, and stages attacks on ISIS gatherings at a distance with silenced sniper weapons. It also engages in kidnapping. Notably, these tactics are not dissimilar from those used by ISIS.

ISIS forces captured Abu Kamal in early July after pitched battles with “opposition battalions and the Al-Qaeda-affiliated Al-Nusra Front terrorist group,” reported Tasnim News. Whether White Shroud is affiliated with Al-Nusra or other opposition groups is unclear.

But there’s plenty of reasons for those living under ISIS rule to take up arms against it. As the New York Timesdetailed in a report from ISIS-controlled Raffa in northern Syria, life under the terror group is hardly charitable. Law and order coexists with threats and the public amputation of the hands of alleged thieves. Women in particular are subject to severe dress codes (see also Christian Caryl, “9 Things to Avoid When Creating Your Own Caliphate“, Foreign Policy, 29.07.2014).

If White Shroud’s tactics at all sounds like terror, it is. Adversaries as extreme as ISIS — and use non-conventional tactics that make them difficult to uproot and defeat — lead to innovation and the development of counter-tactics among their opponents. One famous example is the U.S. recruiting Sunni tribesmen to fight Islamic State in Iraq forces during the Anbar Awakening — by essentially bringing the very communities under siege into the fight.

There are other examples. During the worst years of Colombia’s cocaine-fueled violence in the early 1990s, the vigilante group Los Pepes emerged to conduct a covert war of assassination against associates — and family members — of drug lord Pablo Escobar’s Medellín Cartel. These vigilantes were tacitly supported by Colombian law enforcement. Likewise, Mexico has seen a surge in anti-cartel vigilantes operating outside the control of the state security services.

An insurgent group can blend in and avoid detection from a conventional army, which is relatively easier to detect compared to the insurgent group. But an insurgent group faces similar difficulties fighting another group that flips its own tactics around. While ISIS’s opponents might not be overtly comfortable with a shadowy group assassinating the jihadis with silenced weapons at a distance — what comes around, goes around. But as has been seen in other conflicts, covert violence against the bad guys can often mutate into something worse. Leaders of Los Pepes in Colombia later went on to lead death squads from the country’s right-wing United Self-Defense Forces. Even ISIS initially sprouted up to fight the Assad regime, alongside rebel groups supported by the West.

Tahrir Souri reports White Shroud plans to extend its operations beyond Abu Kamal. That will make the difference between just harassment and a serious threat like the Awakening or Los Pepes.